00:03: Two planes left an airport at noon. One flew east, and the other flew west at twice the speed of the first one. After three hours, the planes were 3,600 miles apart. Find an equation to determine how fast each plane was flying. 00:19: What I'm trying to do here is I'm trying to find an equation in order to solve the problem. I'm not actually going to solve the problem. But in order to find the equation, I need to do a couple of things first. First, I need to determine what information has been given to me. I want to determine my given info. Okay. What do I know? One plane flew east, the other plane flew west going at twice the speed, and then after three hours they're 3,600 miles apart. Okay. I know what I have now, but how am I gonna figure out an equation? Well, I'm going to draw a picture. A lot of times, drawing a picture can just kind of help visualize what is going on, and then the equation will come to you. 01:12: What do I have? I have an airport and I have two planes. One plane flew east, so here is my first plane. And then I have that my second plane flew west, so here is plane two. Now what else do I know? I also know that the second plane was flying at twice the speed of the first one. If I let the first one be "R" then the second plane would need to be "2R". And I'm gonna come over here, and I'm gonna say that R equals the rate of the plane traveling east, just so I don't forget. 02:05: Now, I think I know one other piece of information and that is that at three hours, the distance between them is 3,600 miles after three hours. Looking at that, that kinda helps jog my memory that I have this relationship between distance, rate, and time. And I know that distance equals rate times time. Or let's see, I am trying to determine how fast each plane was flying, so I want rate, so rate equals distance over time. But I don't have R, I have the 2R of the plane traveling west and the R of the plane traveling east. I actually have distance over time equals 2R plus R, because I have after three hours how far apart the two planes were. Let's plug in what we know. Our distance is 3,600 miles, our time is three hours, and that's going to equal 3R. That would be my equation that I would use to determine how fast each plane was flying.

Question

In the example, 2r represents the speed of the plane traveling ________.
Responses
A easteast
B westwest
C northnorth
D southsouth
Question 2
What is the formula for distance?
Responses
A d = rtd = rt
B d = r/td = r/t
Question 3
When you solve the distance formula for rate, you get r = _____.
Responses
A dtdt
B d/td/t
C t/d

Answer 1

Here are the answers to your questions based on the example provided:

1. In the example, 2r represents the speed of the plane traveling B. west.

2. What is the formula for distance?

   • A. d = rt

3. When you solve the distance formula for rate, you get r = _____.

   • B. d/t.